It is easier to teach students
what to think than
how to think. It's also much safer.
For example, Texas' U.S. history book for 11th graders introduces domino theory on page 501. The idea in 1954 was that -- without U.S. intervention -- South Vietnam would fall to Communism, followed by the rest of Southeast Asia, like a line of dominoes.

Twenty years later, that *is* how it turned out. Following North Vietnam's takeover of the South in April 1975, Laos' fragile coalition government collapsed and the Khmer Rouge took over Cambodia. The textbook concludes on page 511 that domino theory played out as predicted.

But is this the right conclusion? To draw a straight line from 1954 to 1975 ignores *everything* the U.S. did in the two decades in-between. Yes, Laos and Cambodia fell to Communism, but was that because we *didn't* intervene or *because we did*?
During the Vietnam War, the United States dropped more tons of explosives on Laos -- on a per capita basis -- than on *any* other country in history, DESPITE the fact they were a neutral party. Even now, "at the current rate of clearance, it would take another 100 years" to clear Laos of all the unexploded ordnance.
[Source]
Would Laos' coalition government still have fallen if we had *not* done that? And what prevented Thailand from suffering the same fate?
Ah, but these questions are too dangerous to ask. Rather than risk students coming to an unpatriotic conclusion, the authors quickly provide the right answer and move on. After all, teachers have a lot to cover.
Thus, we teach students "what to think" rather than "how to think."
And as with all decisions, there are consequences for that choice.